squid: make ipv6 configurable

pkgs/by-name/sq/squid/package.nix

@@ -15,6 +15,7 @@
   systemd,
   cppunit,
   esi ? false,
+  ipv6 ? true,
 }:
 
 stdenv.mkDerivation (finalAttrs: {
@@ -47,7 +48,6 @@ stdenv.mkDerivation (finalAttrs: {
 
   configureFlags =
     [
-      "--enable-ipv6"
       "--disable-strict-error-checking"
       "--disable-arch-native"
       "--with-openssl"
@@ -58,6 +58,7 @@ stdenv.mkDerivation (finalAttrs: {
       "--enable-x-accelerator-vary"
       "--enable-htcp"
     ]
+    ++ (if ipv6 then [ "--enable-ipv6" ] else [ "--disable-ipv6" ])
     ++ lib.optional (!esi) "--disable-esi"
     ++ lib.optional (
       stdenv.hostPlatform.isLinux && !stdenv.hostPlatform.isMusl